Isn't create something your own is a keyboard skill? I don't really like arranger type keyboard due the fact that not many preset I like to play. Having a MPC style keyboard, add many dimension to your music. It demand a lot of creativity,improvisation and planning. Come up something really unique to you. Something like Mark can be done by many people. Just using four chord progression and loop it. Start improvising. Upload to youttube. My instructor who teach me composing already show this in my pop composing course. When I learn piano improvisation, I do need arranger to train a lot of style. Normally, I will switch off chord detection and just run the rhythm preset. With such skill, I enter the DAW world can come with this.
http://www.youtube.com/user/kongwee1978?feature=mhum#p/u/4/OtY6hLHWzx4
Note every note and beat of all instrument are played or key in by me.
But mostly, I do demo for people with this level of arrangement.
Lately, I wanna to do trance, house, dance music more toward kpop.
Being too much in arrangement, I lose my skill to play live fingering piano.
So in the end, keyboard skill is not just about finger.